Two piece beverage cans are becoming more popular and have virtually replaced the three piece can for a number of reasons. Two piece cans do not require soldered side seams and are thus more sanitary for use with food products. They are more appealing aesthetically and are less likely to leak. Beer and beverage cans of the so-called two piece type are currently being produced by the drawn and ironed method. As such, the first operation performed to produce such cans is through the use of a cupping press and a series of conveyors to feed the cups into multiple redraw presses commonly known as wall ironers or body-makers.
Two piece cans are generally blanked and drawn from coil or strip stock and are subsequently redrawn one or more times in order to build the sidewall of the can to a height which can accommodate typically twelve ounces of a beverage. Metal discs are blanked from the coil or strip stock and are punched to produce short cups which then must be conveyed out of the die to a downstream conveyor system which delivers the cups to the redraw presses. These cups leave the stamping dies at great speeds and their light weight and shape make the cups somewhat unstable and difficult to work with.
Prior art conveying devices used for receiving first punched cups for transport out of the die consisted of rubberized mechanical endless belts positioned between the bed of a mechanical press and a lower die shoe. As the cups dropped into position, the conveying belt would move the cups downstream and out of the die to the conveyor system which delivers the cups to the redrawing operation which reduces the diameter of the cup and increases the cup's sidewall height.
Although endless mechanical belts have been used for quite some time and are generally viewed as being reliable in the acceptance and transference of cups from the punch press, it was quite common to experience breakdown in the operation of the mechanical belt. This device was called upon to operate at high speed in a continuous mode, for the normal operation of a can fabricating and handling plant requires an endless supply of cup precursors. If the endless belt or its drive members failed, the consequences could be catastrophic for the entire operation of the plant. Such breakdown would require a termination of the stamping die and punch press, which would terminate the flow of cup stock to the downstream operations of the plant. This could literally result in a plant shutdown, which would last until the conveying device was repaired or replaced.
The use of an air conveyor in a space defined between the bed of a mechanical press and a lower die shoe mounted on the press for removing a succession of cup-shaped objects has been taught in U.S. Pat. No. 4,741,196. Although the invention disclosed and claimed in the referenced patent represented an advance over endless mechanical belts, further improvements to the disclosed air conveyor were envisioned as being desirable. For example, often times, cups dropping onto the conveyor surface are coated with a thin layer of oil as a result of the sheet stock moving through the mechanical press assembly. This oil can result in thin film adhesion between the cup and upper surface of the air conveyor or plenum. In addition, the nozzle for expelling compressed air parallel to the conveyor surface was taught in U.S. Pat. No. 4,741,196 to be a simple louvered outlet which was found to be inefficient in moving the cup-shaped objects in a downstream direction along the plenum.
It is thus an object of the present invention to provide a device for conveying cup-shaped objects, such as the bodies of two piece cans, without the use of any moving parts.
It is yet another object of the present invention to provide a device for conveying cup-shaped objects, such as the bodies of two piece cans, through the use of directionally applied pressurized air without experiencing instability or part turbulence throughout the length of operation of the conveying device.